add more refs to browser-related bugs in Less comments

less/close.less

@@ -23,6 +23,7 @@
   // Additional properties for button version
   // iOS requires the button element instead of an anchor tag.
   // If you want the anchor version, it requires `href="#"`.
+  // See https://developer.mozilla.org/en-US/docs/Web/Events/click#Safari_Mobile
   button& {
     padding: 0;
     cursor: pointer;